In order not to change a gas outlet and a gas inlet of a system in refrigerating and heating processes for a two-pipe multi-split air-conditioner in the related art, inlet and outlet pipes of a compressor are connected to ends of a four-way valve, and more valves are required to perform a two-pipe function, and thus the multi-split system may have a complex internal structure and many blind pipes appears in a flow passage of the system in the refrigerating or heating process.